Insulator



Patented June 17, 1930 UNITED STATES PATENT OFFICE HOUSE ELECTRIG &MANUFACTURING COMPANY, A CORPORATION VANIA 0F PENNSYL- INSULA'IORApplication filed April 2, 1927.

My invention relates to insulators and particularly to insulatorssubject to cantilever loads, such as those for supporting bus-bars,switches and the like.

One object of my invention is to provide a device of the above-indicatedcharacter that shall so convert cantilever load forces into compressionforces as to provide a more effective insulator than those heretofore employed and one that is less subject to damage.

Another object of my invention is to provide a bus-bar or similarinsulator, subject to cantilever load, that shall utilize the advantages of fibrous insulating material under tension and refractoryinsulating material under compression.

Another object of my invention is to pro vide an insulator that shall soembody a relatively-short and small-diameter fibrous strain rod and alonger refractory insulating tube of considerably greater diameter as tofacilitate the conversion of cantilever load forces into compressionforces, to provide a stable base for the insulator and to utilize thesurface-creepage distance of the refractory tube to maximum advantage.

Another object of my invention is to provide an insulator that shallembody a tubular insulating member of relatively great diameter or basearea for co-operation with a main supporting structure, and a singlemeans for holding a conductor, converting cantilever load forces intocompression forces and mounting the insulator.

' Another object of my invention is to pro vide an insulator that shallcomprise parts of such relation and simple form as to great-- lyfacilitate the manufacture and assembly thereof. l

A further object of my invention is to provide an insulator that shallbe compact and durable in construction, economical to manufacture andeffective in its operation.

' In insulators for supporting bus-bars and other conductors in suchposition and relation as to subject the same to cantilever loads,damage, caused by bending tendency of the insulators, frequently occursand, in insulators embodying refractory or similar hard brittlematerial, this damage usually Serial N0. 180,442.

occasions break down of the insulator, With the resulting economicalloss in labor and material, as well as the interruption of service.

Insulators of the character specified above have also, usually, embodiedterminal members or end caps Which shorten the surfacecreepage distancethereof. Accordingly, in practicing my invention, I provide a refractoryinsulating member that is so Worked in compression, a fibrous insulatingmember that so shares the load and assists in converting the cantileverforces into compression forces in the refractory member and otherfeatures that are so combined and related to the refractory and fibrousmembers as to overcome the objectionable features of prior insulatorsand to attain the objects set forth above.

The single figure of the accompanying drawing is a side View, partiallyin section and partially in elevation, of an insulator constructed inaccordance With my invention. 5

The device comprises, in general, an outer tubular shell or protectivemember 2, a strain insulator therein comprising an insulating rod ormember 3 and metal end or terminal structures 4, end closure members 6for the shell 2, cushioning and sealing means 7 between the shell 2 andthe endclosure 6, nuts 9 and lock Washers 10 for holding the end-closuremembers 6 in position and a body 12 of insulating filler mate rial inthe shell 6 about the strain insulator 3 and portions of the terminals 4thereof.

The shell 2, preferably of refractory insulating material, such asporcelain or glass, is formed as a cylindrical tube having ends that arepreferably flat or substantially normal to the longitudinal axis of thetube corrugated outer surfaces 14 and inner surfaces 15 that are slopedto render the tube slightly thicker at its mid portion than at its ends.

The rod 3, of fibrous insulating material, such as Wood, impregnatedpaper or cloth, molded composition or other suitable material, ispreferably provided With substantially frusto-conical ends 17 and anannular co-operate With, the ends of the strain inthe corrugatedintermediate portion 18 that is thicker at its central section than atthe lesser bases of the frusto-conical ends 17. The lateral extreme endsurfaces of the member 3 are offset from the corresponding end surfacesof the shell 2. Each of the terminal structures 4 preferably comprises aportion 20, initially of substantially straight-sided cup-shape, that isswaged in position over 'one of the frustoconical ends-17 and ascrew-threaded shank portion 21 on which one of the nuts 9 is mounted. 1

Each end-closure member 6 is referably constructed of yieldable or resilent sheet material, such as sheet steel having a suitable coatingthereon, to beof substantially discoidal character having substantiallyparallel-plane offset inner and outer portions23 and 24 that aredisposed over, and

sulator 3 and the shell 2, respectively.

This construction provides a space, between the end of the straininsulator 3 and the end of the shell 2, for the nut 9 and the lockwasher 10 or other suitable holding means co-operating between the'shank21 and the end-closure member 6, whereby space is conserved and theinsulator is provided with suitable end areas for stable mounting of theinsulator and stable mounting of 'a bus-bar or other structure on theinsulator. V i i The end disks or plates 6 are also so biased inwardlyon the insulator 3 against askets 7 and shell 2 by the nuts 9 as to pace the shell 2'in compression and to effect a strong seal against theescape of the filler material 12.

In the above-described structure, the strain insulator or rod 3,together with its end terminal members .3, constitute a single means forholding a bus-bar or other conductor, for. assisting in convertingbending forces into compression forces in the shell 2 andffor holdingthe entire insulator to a main stationary supporting structure (notshown) at a single position between the insulator andsthe mainsupporting structure. This position is along, and closely adjacent to,the base-end shank 21, in contr'adistinction to prior-art structureshaving a plurality of bolts distributed about the perimeter of theinsulators at the, base ends thereof. e

Further, since the members 6 are of discoidal form and do not'extend'along the outer surface of the shell 2, as in prior practhe fullinsulating value of thesurface 14 is obtained, giving greater effectivelength to the insulator for the same amount of material. v r V Inoperation, with one end of the insulator fixed to the main supportingstructure, cantilever load at the other end thereof tends to bend thestrain insulator near the main support. This tendency biases the outerplate 6 against the shell 2, whereby the latter, in addition to thecompression effected therein by the plates 6, as above described,issubjected to load compression. The shell 2 is, therefore,.relativelyfree of any forces except compression forces and is therebyoperatedunder its best condition.

By m'y-invention, an insulator is provided that embodies arts of simplemanufacture and easy assem ly which are operated'under vadvantageousconditions and are protected against damage. The device is also adaptedfor the readymounting thereof and the reception thereon of the conductorwhich it is to support, is rugged and durable, is effective inoperation, and is, in general, an improvement over similar devicesheretofore employed,

'While I have shown and described a particular form of my invention,changes may be effected therein without departing from the spirit andscope thereof, as set forth in the appendedclaims.

. I claim as my invention:

1. An insulator subject to cantilever load comprising a tubularinsulating shell of relatively large diameter and short length,oaninsulating strain rod therein ter compared to the diameter of the shelland having ends inwardly offset from the ends of the shell, means forclosing the ends of the shell and converting cantilever load forces ofthe rod into compression forces in the shell including end plates havingperiof small diamethe ends of projecting through K 2; An insulatorcomprising a tubular in:

sulating member, a strain insulator disposed therein with'a-nend'inwardly offset from an end of the tubular member and an end-closuremember of discoidal sheet-material character having its outer perimeterco-operating with the end of the tubular member and a depressed centralportion co-operating with the end of the strain insulator. i

3. An insulator comprising a tubular insulating member, astraininsulator disposed therein with an end inwardly offset froman endof the tubular member and an end-closure member of discoidal resilientsheet-materialcharacter having its outer perimeter over the end of thetubular member and its central portion flexed inwardly and fixedto thestrain insulator. 4. An insulator comprising a tubular insulatingmember, a strain insulator disposed therein with an end inwardly oflsetfrom an end of the tubular member, an end closure member of discoidalsheet-n'iaterial characterhaving substantially parallel-plane ofl'setportions over said ends and means in the space provided by the offsetportions of the disk for securing the disk to the strain in sulator.

5. An insulator comprising a tubular insulating member, a straininsulator disposed therein with an end inwardly offset from an end ofthe tubular member and a terminal shank projecting outwardly beyond saidtubular end, an end closure member of discoidal sheet-material characterhaving substantially parallel-plane offset portions over said ends andmeans in the space provided by the offset portions of the diskcooperating between the shank and the disk for holding the disk inposition.

6. An insulator comprising a tubular in sulating member, a straininsulator disposed therein with an end inwardly offset from an end ofthe tubular member and a terminal shank projecting outwardly beyond saidtubular end, an end closure member of discoidal sheet-material characterhaving substantially parallel-plane offset portions over said ends, ayieldable gasket between the discoidal and tubular members andlocking-nut means on the shank in the space provided by said offsetportions of the disk for holding the disk in position.

7. An insulator comprising a refractory insulating tube having slopinginner surfaces and walls of longitudinallywarying thickness, a fibrousstrain insulator therein having its ends inwardly offset from the endsof the tube, meta terminal members having portions secured to the endsof the strain insulator and shanks projecting be yond the ends of thetube, discoidal metal members having offset substantially parallel-planeportions over the ends of the tube and strain insulator, means withinthe outer planes of the disk for holding the disks in position and aninsulating filler medium surrounding the strain insulator in the tube.

8. An insulator comprising a refractory insulating tube having flatends, a fibrous strain insulator therein having its ends inwardly offsetfrom the ends of the tube, metal terminal members having cup-portionssecured in position over the straininsulator ends and shanks projectingbeyond the ends of the tubular member, sheet-metal disks havingparallel-plane offset portions over the ends of the tube and straininsulator, means in the spaces provided by said offset disk portionseo-operating etween the disks and the shanks for holding the disks inposition and a body of insulating material filling the remaining spacein the tube.

9. An insulator comprising a refractory insulating tube having flat endsand corrugated outer side surfaces, a wood strain insulator disposedtherein having corrugated sides and frusto-conical ends inwardly offsetfrom the ends of the tube, metal terminal members having cup portionsswaged in position over said frusto-conical ends and screw-threadedshanks projecting beyond the ends of the tubular member, sheetmetaldisks having parallel-plane offset portions over the ends of the tubeand strain insulator, lock washers and nuts in said shanks in the spacesprovided 'by said offset disk portions, yieldable gaskets between thetubular member and the disks and a body of insulating material fillingthe remaining space in the tubular member.

10. An insulator subject to cantilever loads comprising a refractoryinsulating tube of relatively large diameter and short length havingflat ends and corrugated outor side surfaces, a fibrous insulatingstrain rod therein of small diameter compared to the diameter of thetube and having substantially frusto-conica-l ends inwardly offset fromthe ends of the tube, metal terminal members having cup portions swagedin position over said frusto-conical ends and screw-threaded shanksprojecting beyond the ends of the tube, means for closing the ends ofthe tube and converting cantilever load forces of the rod intocompression forces in the tube including apertured sheet-metal diskshaving substantially parallelplane ofl'set portions over the ends of thetube and the rod, yieldable gaskets between the disks and the tube,locking nut means on the shanks for holding the disks and an insulatingfiller material in the tube.

In testimony whereof I have hereunto subscribed my name this 30th day ofMarch, 1927.

EViUJlER H. SCHRAMM.

